Fuel system for dual use gas turbine engine main fuel pump

A system comprising:

• a main pump having a main pump shaft configured to connect to a gear box for driving the main pump with rotational power from the gear box in a run mode, and for driving the gear box with rotational power from the main pump in a start mode;
• a first fuel line with an inlet configured to be connected in fluid communication with a fuel source, wherein the first fuel line includes a first branch in fluid communication with the main pump, and a second branch;
• a start pump connected in fluid communication with the second branch of the first fuel line;
• a second fuel line connecting the start pump in fluid communication with a pump management valve (PMV);
• and
• a third fuel line connecting the main pump in fluid communication with the pump management valve;
• and
• wherein the PMV is connected in fluid communication with the second fuel line, with the third fuel line, and with a fourth fuel line, wherein the fourth fuel line has an outlet configured to be connected to supply a downstream fuel system, wherein the PMV has a first state connecting the second fuel line in fluid communication with the third fuel line in the start mode to drive the main pump with flow pressurized by the start pump, and a second state connecting the third fuel line in fluid communication with the fourth fuel line for supplying fuel from the main pump to the outlet of the fourth fuel line in the run mode;
• and
• wherein in a regeneration sub-mode of the run mode, the PMV connects the third and fourth fuel lines in fluid communication to bypass flow from the main pump back to the main pump through a fifth line and through the start pump, for electrical energy recovery by using the start pump to drive an electric machine for electric power generation.